Discussion
Abdominal reconstruction in the contaminated or potentially-contaminated abdomen is challenging because of the high risk of re-infection and hernia recurrence. Surgical techniques, synthetic meshes, and biologic graft materials that allow for complete restoration of the midline fascia have been developed to improve outcomes in these patients. For example, in a study comparing suture repair of incisional hernia to mesh repair, it was found that "mesh repair results in a lower recurrence rate and less abdominal pain and does not result in more complications than suture repair" after long term follow-up. In this series, we demonstrate that components separation and midline reinforcement with a variety of graft materials in Grade III and Grade IV hernias is safe and feasible with low morbidity and a low risk of medium-term recurrence.
The VHWG classification was used in this study as we feel it identifies high risk patients and those in which we could consider to use a biological mesh. The European Hernia Society (EHS) have published their own classification which includes the location and size of the hernia defect; however the potential contamination and infection risk is not mentioned. A combination of the VHWG and EHS classification would enable an incisional hernia to be fully described; however in our subgroup of patients, all with large, complex hernias, the emphasis was on the potential of contamination. In 7 patients, we determined that the risk of post-operative surgical site infection was so high that we opted to place Collatamp®G, a fully resorbable collagen "sponge" impregnated with high doses of fast-release gentamicin for local delivery of broad spectrum antibiotic, prior to abdominal wall closure.
Reconstituting the midline is an important step in the repair to reduce recurrence; we achieved this in 87% of all patients. A variety of reconstruction techniques have been described in the literature. The Ramirez technique is common and successfully allows separation of the abdominal wall components for rectus advancement and achieves closure of the midline in 80% of cases. In larger or complex hernias it is sometimes necessary to adopt double-breasting of the fascia techniques and other methods to gain more width. The importance of achieving midline closure has been demonstrated recently by Itani et al who prospectively followed 80 patients undergoing Grade III or IV hernia repair using components separation and biologic mesh reinforcement and found the recurrence rate was increased if the midline wasn't closed. Similarly, another study of large incisional hernia repairs using polypropylene mesh showed a recurrence rate of 44% using an inlay bridging technique as compared to only 12% when an underlay reinforcement was used. Reinforcing the reconstruction with mesh has also been shown to reduce recurrence rates; the mesh can be placed as an onlay, sublay or inlay.
In this series, 7 out of 23 patients had the recommended sublay mesh; therefore the majority had midline closure and an onlay mesh. Sublay mesh was described by Rives in 1973 as a retromuscular or preperitoneal mesh and is the preferred position because of reduced wound complications and low recurrence rates. In patients who have undergone multiple surgery it is often not feasible to create space for a sublay mesh. If the midline can be closed, an onlay mesh has been shown to be effective, with an 18.5% recurrence rate at 10 years. We feel the most important step to reduce recurrence is to achieve midline closure regardless of the location of mesh reinforcement.
An inlay mesh or 'bridging mesh' is to be avoided if at all possible because serious complications, such as adhesion formation, fistulation and hernia recurrence, have been reported.
Various mesh types are available and can be classified as either biologic or synthetic. Within these two classifications, meshes can further be classified as either non-absorbable or absorbable, and biologic meshes may also be classified as human-derived or animal-derived. While synthetic surgical meshes have been used successfully for many decades, complications associated with adhesion, erosion, persistent infection, persistent inflammation, fistula formation, seroma formation, and hematoma are common. Additionally, they are relatively contraindicated for use in Grade III and Grade IV hernias due to the risk of chronic infection. For example, Kapiris et al reported 282 cases of seroma and hematoma formation in 3530 hernias (8%) repaired with polypropylene mesh using the transabdominal (TAPP) approach, and Bingener et al noted adhesion formation in 35% of patients following laparoscopic ventral incisional hernias repair with polypropylene mesh.
Initially, we used synthetic mesh in 6 patients but more recently, we have chosen to use biologic graft materials in Grade III and Grade IV hernias due to recommendations made by the VHWG. Biologic mesh materials have been introduced to the market in an attempt to minimize the complications associated with synthetic materials. Examples of biologic surgical meshes include Peri-Guard® (Synovis), Permacol® (Covidien), AlloDerm® and Strattice® (Life Cell), and Biodesign® (Cook). Peri-Guard, Permacol, Strattice and Biodesign products are manufactured from collagen obtained from animal tissues, while AlloDerm is derived from human dermal tissue. The Peri-Guard and Permacol products have been cross-linked using chemical methods to minimize immunogenicity and to make them more resilient in the face of contamination. The Biodesign, Strattice and AlloDerm surgical mesh products are not cross-linked and are often associated with remodelling of new tissues.
While not specifically indicated for use in Grade III and Grade IV hernias, biologic meshes may minimize the adverse events seen with synthetic materials because they more closely recapitulate the natural tissue environment into which they are placed. These natural tissue meshes can be fabricated to integrate quickly with the patient's tissues, allow rapid angiogenesis to allow the patient to combat infection and stimulate the deposition of additional host connective tissue, optimizing tissue restoration in ways that synthetic mesh materials are unable. Additionally, in the contaminated abdomen, many of the biologic meshes do not have to be removed in the face of infection.
The most common post-operative complication that we experienced in our series with biologic graft materials was transient seroma formation following implant. While most of these seromas are associated with the level of complexity of the dissection and repair, they often resolve, but can cause patient discomfort and impair the healing process. In order to minimize the extent of seroma formation, we now routinely employ the use of 2–3 drains that are left in place above and below the graft reinforcement until daily fluid output is less than 25 ml. A study of 37 patients undergoing repair of enterocutaneous fistula and abdominal reconstruction reported an anastomotic leak in 4 out of 37 and a hernia recurrence rate of 32%, in our series there was no anastomotic leaks and a hernia recurrence rate of 12.5% in the enterocutaneous fistula patients (1 out of 8).
The low incidence of recurrence and complications in this series prevents us from clearly assessing the effect of mesh type or location on outcomes. A larger series examining these variables is warranted.